A person in jail that gets mail.
An inmate looks at their cell mate and asks what they have in their hands.
Cell mate replies: I just got received a letter. I just love getting jail mail.
420 is a code number for marijuana. So therefore, a 420 pipe simply means a marijuana pipe.
Hey man, I'm gonna smoke some 420 in my 420 pipe, you should join me.
Death Needle
Death needle aka lethal injection, is what death row inmates receives. It can also mean being used to shoot up drugs that led to death due to an overdose.